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Hawaii Researcher Fertilizes Rabbit Eggs

Posted on: Tuesday, 9 March 2004, 06:00 CST

A University of Hawaii researcher whose team pioneered the cloning of mice six years ago has achieved another scientific first - fertilizing rabbit eggs with freeze-dried rabbit sperm.

The method used by Ryuzo Yanagimachi produced a live rabbit, the first live birth of a mammal other than a mouse, from freeze-dried sperm, said Stefan Moisyadi of the Institute for Biogenesis Research in the John A. Burns School of Medicine

The full-term pup was born, but eventually died because its mother did not care for it, said Yanagimachi, a professor of anatomy and reproductive biology, and the institute's director.

Yanagimachi developed freeze-dried sperm technology to make live mice in 1998, the same year he and his team became known in the science community worldwide for cloning generations of mice.

In his freeze-dried process, sperm are technically dead, but the nucleus is viable and results in live births.

Yanagimachi headed the reproductive biologists who fertilized rabbit eggs with freeze-dried rabbit sperm along with Xiangzhong Yang, of the Department of Animal Science/Center for Regenerative Biology at the University of Connecticut.

It was more difficult to freeze-dry mouse sperm because rabbits are more like humans, Yanagimachi said. The similarity suggests freeze-drying could be used to preserve sperm from humans and other species, he said.

Freeze-drying breaks plasma membrane and causes fragmentation of sperm tails, but while the cell is dead, the DNA remains intact, he said.

Because UH didn't have a facility for rabbit experiments, the sperm was freeze-dried at his lab and sent to the University of Connecticut, Yanagimachi said.

After 230 eggs were fertilized with freeze-dried sperm, some of the embryos were transplanted into eight female rabbits.

Of those, one pup was born. The baby rabbit's death because of maternal neglect often happens in single-birth pregnancies in species that usually give birth to multiple offspring, the scientists said.

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